This invention relates to a motor control system for a telescope, usable, for instance, in controlling the position of the viewing assembly or telescope tube in the telescope. As herein disclosed, the control system is employed in making adjustments in the declination of the viewing assembly. In disclosing the invention in this context, however, it is not intended to preclude application of the invention in the making of other adjustments where smooth, vibration-free operation is desired.
A common form of mounting for an astronomical telescope embodies a two axis system, comprising an inclined rotation axis, which parallels the earth's rotation axis, and a second horizontal rotation axis, which intersects the inclined axis at right angles to a vertical plane containing the latter axis. The inclined axis is referred to as the polar axis, and the horizontal axis is referred to as the declination axis. Rotation of the telescope tube or viewing assembly about the declination axis adjusts the elevation of the telescope tube to correspond to the latitude at which the telescope is used.
Adjustments in declination are generally accomplished utilizing a knob attached to a lead screw, which operates a tangent arm incorporated in the telescope that is connected to the viewing assembly or telescope tube. These adjustments may be done manually. But, an electric motor facilitates the adjustment, and this is especially true when the telescope is used with video cameras and the like where smooth, vibration-free operation is imperative. Whenever a telescope is used with a time exposure camera, it is absolutely necessary to have a motor operate the lead screw, since a slight touch of the hand to the telescope produces movement impairing the picture due to the high magnification involved.
In my prior issued U.S. Pat. No. 4,709,178, there is disclosed a motorized drive attachment for installation with a telescope, particularly adaptable to make adjustments in the declination of the telescope tube in the telescope, and which features a flexible and resilient clamp that snap fits over a frame portion in the telescope. The clamp mounts the housing of a motor and the output shaft of the motor connects through a coupler with a rod which produces declination adjustment. The drive attachment described provides a relatively simple way for incorporating a motor control system into a telescope for making adjustments therein. However, in some types of telescopes the geometry of the frame in the telescope is such that the clamp structure described will not always provide a satisfactory mounting for the motor. Other motor systems that have been proposed have included exposed gearing or drive belts, with the belts involved being prone to wear and tending to fall off during use and the gears tending to bind or grind with operation of the motor. Furthermore, with a system which involves a motor attached in a substantially permanent manner to the telescope frame and driving a control rod through gears or belts, the position of the motor is such that the telescope, without removal of the motor, is prevented from fitting with the carrying case intended for moving the telescope from one place to another. This obviously is inconvenient, as it means either that the case can't be used, or if the case is used, that the motor and its mounting be removed with unscrewing of screws and disconnecting of belts before the telescope is fittable into the case.
A general object of this invention is to provide improvements in a motorized drive attachment for a telescope featuring a slip-on type of mounting for the housing of the motor, the mounting accurately positioning the motor with the parts mounted in place, but permitting the motor and its housing readily to be disconnected and removed in the event, for instance, it is desired to move the telescope using its telescope case. A relatively small mounting bracket may be secured, as by screws, etc., to the frame of the telescope, and in the usual instance this need not be removed from the telescope in the event that it is desired to move the telescope from one place to another.
Another object is to provide a motorized drive attachment as above described and with a slip-on type of mounting for the housing of a motor in the attachment, where the mounting includes concentric sleeves establishing a mounted position for the motor and its housing in the attachment. One sleeve is secured to the housing of the motor and the other sleeve is mounted in an appropriate manner on the frame of the telescope. With the sleeves arranged so that one is supported on the other, the motor shaft of the motor becomes axially aligned with and coupled to the control shaft of the telescope. With the sleeves separated one from another by relative axial displacement, the motor, its housing and sleeve becomes a separate assembly, leaving essentially only the other sleeve as a residual on the telescope. This portion takes little space and in most instances will not interfere with the packaging of the telescope for movement from one place to another. The attachment contemplated is readily installed on a telescope, with accurate positioning of the drive shaft of the motor and the control shaft of the telescope.